While Iím aware that Catless DPís arenít meant for street, most still seem to use them. Also the likelihood of the RTA stopping you and getting under your car is pretty slim. Iím assuming the only situation that would have you concerned with running them would be if you have to roll over the pits / car inspection.

This brings me to under bonnet mods. In some states, DCIís and BOVís are illegal and the likelihood of being stopped and having the RTA look under the bonnet is obviously higher. We could bring meth into this too, but it doesnít seem to be as common in Aus.

My concern: If youíre stopped and found to have DCIís and/or a BOV, in addition to a fine, itíll likely lead on to a full inspection too. This could lead to the discovery of catless DPís Ė no?

So now Iím thinking, would one be better off with a drop-in filter and DVís instead of DCI and bov, as they would decrease the chance of being pinged should the RTA pop your bonnet. And secondly (probably a stupid question) if you were ordered to have a full inspection, would you remove the catless dpís prior Ė given how much of a PITA they are to remove.

This sort of leads onto a side question; since 335i's run dual cats (primary and secondary) Ė is anyone aware of the ruling with only running secondary? Are we able to run bigger cats in place of the secondaries, or it doesnít work like that? I remember reading somewhere that an ADR approved cat would be legal, so it the secondary cat ADR approved??

You're correct in regards to intake and bov, you would be much safer with a high flow filter in an enclosed intake (oem) and dv's.

As pavo has stated anything not oem is illegal (even if you have an engineers cert the cop can still slap you with a canary)

Regards to the catless DP's if your exhaust was excessively loud then they may ping you to have an epa test for emissions, then upon testing for emissions you may run into emission issues (i.e if you fail I believe they give you another crack - albeit at your expense again but there are a few dirty tricks to ensure the emissions test passes)

So in a nutshell if you're worried about cops stick with the oem intake with a bmc/K&N panel filter and forge dv's and go with the catless DP's and retain the oem muffler setup but tbh euro cars rarely if ever get pulled over in defect stations its the wrevolines that get targeted unless you're driving like a cock in a suburban area and asking for trouble.

Look at the vast numbers of jap import cars on the roads on Australia that are just defects on wheels. Look at all the tard p-platers with fart cannon exhausts, hid bulbs in reflector lamps, cats cut out, cut springs, exposed pod filters, dodgy body kits, the list goes on. The cops would have their arms full with these as they are the most blatant cases (even though I doubt they really apply enough heat on these morons). A recent model BMW being driven by someone that doesn't look like they are a crim isnt going to raise suspicion.

Good questions and also ones that I am pondering myself. Personal experience here in the ACT has shown that cone intakes seem to get the OK at rego inspections. I had bought a E36 M3 with a cold air intake and a cone filter. Went through without issues. The NSW guy who bought it off me had no end of troubles getting it registered until he fabricated a cover for it; passed no problems after that. Seems like open cone intakes are frowned upon in NSW. I should stress again, this has been my experience.

I have to agree with the comment that if you are concerned, then maybe mods like higher flow sealed intakes and oem style DVs are the 'safer' option.

- RTA won't be the one pulling you over, it'll likely be HWP or general duty police.
- If they see a DCI you could get a defect which you'll have to get cleared by someone on the rta's list of registered mechanics. When you put your stock airbox on, the mechanic will see the DCI has been removed and most likely give it a tick and you're off on your way. Unlikely (time/effort constraints) the mechanic will then go inspect everything on your car.

If for some reason you ever got a full shakedown and had to report to the pits for a thorough vehicle inspection then I would put the stock cats in... for $500 install, consider it 'insurance' against a potentially much larger fine.

Now away from all these scary stories, who here has ever been defected in a BMW OR been asked to open their bonnet?

My question is would the person or police even know what to look for outside the exposed intake. I doubt they'd immediately identify a bov or downpipe. Just cover the filters.

They definately wouldn't spot the DP's but the bov yup they would for sure! My chargepipe is anodised black but the bov is pretty obvious (the plod actually get trained on what mods to look for in a engine bay believe it or not)

Been pulled over by the police (VIC) a few times... they have NEVER asked to look in the engine bay

late model european cars apparently don't get modified... or more likely, the cop has very limited experience in dealing with these cars and doesn't really know what he's looking for / is not sure what is OEM and what isn't anyway

Been pulled over by the police (VIC) a few times... they have NEVER asked to look in the engine bay

late model european cars apparently don't get modified... or more likely, the cop has very limited experience in dealing with these cars and doesn't really know what he's looking for / is not sure what is OEM and what isn't anyway

LMFAO I like how you drop the "been pulled over by the fuzz a few times" and just sail on...